Shinji Higa

Flavonoids such as luteolin, fisetin and apigenin are inhibitors of interleukin-4 and interleukin-13 production by activated human basophils.

Background: We have previously shown that fisetin, a flavonol, inhibits IL-4 and IL-13 synthesis by allergen- or anti-IgE-antibody-stimulated basophils. This time, we investigated the inhibition of IL-4 and IL-13 production by basophils by other flavonoids and attempted to determine the fundamental structure of flavonoids related to inhibition. We additionally investigated whether flavonoids suppress leukotriene C4 synthesis by basophils and IL-4 synthesis by T cells in response to anti-CD3 antibody. Methods: Highly purified peripheral basophils were stimulated for 12 h with anti-IgE antibody alone or anti-IgE antibody plus IL-3 in the presence of various concentrations of 18 different kinds of flavones and flavonols. IL-4 and IL-13 concentrations in the supernatants were then measured. Leukotriene C4 synthesis was also measured after basophils were stimulated for 1 h in the presence of flavonoids. Regarding the inhibitory activity of flavonoids on IL-4 synthesis by T cells, peripheral blood mononuclear cells were cultured with flavonoids in anti-CD3-antibody-bound plates for 2 days. Results: Luteolin, fisetin and apigenin were found to be the strongest inhibitors of both IL-4 and IL-13 production by basophils but did not affect leukotriene C4 synthesis. At higher concentrations, these flavonoids suppressed IL-4 production by T cells. Based on a hierarchy of inhibitory activity, the basic structure for IL-4 inhibition by basophils was determined. Conclusions: Due to the inhibitory activity of flavonoids on IL-4 and IL-13 synthesis, it can be expected that the intake of flavonoids, depending on the quantity and quality, may ameliorate allergic symptoms or prevent the onset of allergic diseases.

Interleukin-18 Is Elevated in the Sera from Patients with Atopic Dermatitis and from Atopic Dermatitis Model Mice, NC/Nga

Background: Several lines of in vitro and in vivo studies have demonstrated that interleukin-18 (IL-18) shows both antiallergic and allergy-promoting activities. But its expression in allergic diseases remains unknown. Methods: Serum IL-18 levels from atopic dermatitis (AD) model mice, NC/Nga and control mice and from patients with AD and healthy volunteers were measured by ELISA. The relationship between IL-18 levels and serum IgE levels or clinical severity was also examined. Results: Serum IL-18 levels from NC/Nga mice were significantly increased compared to those from control mice. The elevation of IL-18 in the sera was observed prior to the onset and during the development of dermatitis in NC/Nga mice. In addition, IL-18 levels in the sera from patients with AD were significantly (p < 0.05) elevated compared to those from healthy volunteers. However, serum IL-18 levels tended to correlate negatively with serum IgE levels in patients with AD and NC/Nga mice. Conclusion: IL-18 is overexpressed in AD.

Oral administration of persimmon leaf extract ameliorates skin symptoms and transepidermal water loss in atopic dermatitis model mice, NC/Nga

Summary Background  We have previously shown that persimmon leaf extract and its major flavonoid constituent, astragalin, inhibited histamine release by basophils and that oral administration of these substances prior to the onset into an atopic dermatitis (AD) model mouse, NC/Nga, prevented development of dermatitis.

Interleukin-18 enhances the production of interleukin-8 by eosinophils.

Interleukin‐18 (IL‐18), a proinflammatory cytokine, leads to IFN‐γ production by NK or T cells, induces Th1 differentiation and suppresses IgE synthesis by B cells when acting on responding cells together with IL‐12. IL‐18 also exhibits biological activities related to allergic inflammation such as histamine or IL‐4 release from basophils and accumulation of eosinophils in localized lesions in allergic model mice. In this study, Reverse transcription (RT)‐PCR analysis revealed that IL‐18 receptor α chain mRNA was expressed in both freshly prepared eosinophils and two eosinophilic cell lines (YY‐1 and EoL‐1 cells). Flow cytometry and RT‐PCR analyses revealed that the treatment of YY‐1 cells with n‐butyric acid promoted cell maturation and caused an enhancement of IL‐18 receptor α chain expression. IL‐18 had little effect on the survival of peripheral eosinophils, but it dose‐dependently augmented IL‐8 synthesis by YY‐1 cells. In addition, IL‐18‐mediated up‐regulation of IL‐8 expression in eosinophils from a patient suffering from hyper‐eosinophilic syndrome was confirmed. Our findings using peripheral blood eosinophils and eosinophilic cell line suggest the functional importance of IL‐18 in the induction of IL‐8 and a potential proinflammatory role in allergy.

Luteolin, a Flavonoid, Inhibits CD40 Ligand Expression by Activated Human Basophils

Background: We have previously shown that flavonoids such as luteolin, apigenin and fisetin inhibit interleukin 4 and interleukin 13 production. In this study, we investigated whether luteolin can suppress CD40 ligand expression by basophils. Methods: A human basophilic cell line, KU812, was stimulated with A23187 and phorbol myristate acetate (PMA) with or without various concentrations of luteolin or other flavonoids for 12 h, and CD40 ligand expression was analyzed by FACS. The effect of luteolin on CD40 ligand mRNA expression was studied by semiquantitative reverse transcription PCR analysis. In addition, CD40 ligand expression was also measured in purified basophils that had been stimulated for 12 h with A23187 plus PMA with or without various concentrations of luteolin. Results: CD40 ligand expression by KU812 cells was enhanced noticeably in response to A23187 and even more strikingly augmented by A23187 plus PMA. The expression was significantly suppressed by 10 or 30 µM of luteolin, whereas myricetin failed to inhibit. Reverse transcription PCR analyses demonstrated that luteolin inhibited CD40 ligand mRNA expression by stimulated KU812 cells. Of the six flavonoids examined, luteolin, apigenin, fisetin and quercetin at 30 µM showed a significant inhibitory effect on CD40 ligand expression. The incubation of purified basophils with A23187 plus PMA significantly enhanced CD40 ligand expression, and the presence of luteolin again had an inhibitory effect. Conclusions: Luteolin inhibits CD40 ligand expression by activated basophils.

Administration of anti-interleukin 18 antibody fails to inhibit development of dermatitis in atopic dermatitis-model mice NC/Nga

Summary Background Interleukin (IL)‐18 has been shown to activate basophils to produce histamine and IL‐4 and to induce naive T cells to differentiate into T‐helper (Th) 2 cells. However, when expressed together with IL‐12, IL‐18 induces Th1 cell development and inhibits IgE synthesis. Previously we reported that serum IL‐18 levels were elevated in the sera from atopic dermatitis‐model mice NC/Nga, prior to the onset and during the development of dermatitis.

Effect of enzymatically modified isoquercitrin, a flavonoid, on symptoms of Japanese cedar pollinosis: a randomized double-blind placebo-controlled trial.

Background: Flavonoids exert antiallergic and antioxidant effects. We investigated the efficacy of enzymatically modified isoquercitrin (EMIQ), a flavonoid, to relieve symptoms of pollinosis. Methods: In a parallel-group, double-blind placebo-controlled study design, 20 subjects with Japanese cedar pollinosis took two capsules daily of 100 mg EMIQ or a placebo for 8 weeks during the pollen season. Subjective symptoms and activities of daily living (ADL) scores were recorded every day, and the quality of life (QOL) score was obtained every 4 weeks. Blood sampling was performed before and after the study to measure serum cytokines, chemokines, IgE, quercetin and oxidized biomarkers. Results: During the entire study period, total ocular score and ocular itching score for the EMIQ group were significantly lower (p < 0.05) than for the placebo group. When limited to the individual periods, total symptom score for the EMIQ group was significantly lower (p < 0.05, week 4–5) than that for the placebo group while other scores for the EMIQ group, such as total nasal score (p = 0.06, week 4–5), nasal obstruction score (p = 0.08, week 4–5), lacrimation score (p = 0.06, week 5–6), ocular congestion score (p = 0.08, week 4–7) and ADL score (p = 0.08, week 4–7), all tended to be lower. The levels of serum cytokines such as interleukin (IL)-4, IL-5, IL-12, IL-13, interferon-γ, and eotaxin and IgE were not significantly downregulated by the intake of EMIQ but the serum concentrations of oxidized low-density lipoprotein and thymus and activation-regulated chemokine were reduced. Conclusion: Intake of the quercetin glycoside EMIQ was safe and influenced ocular symptoms caused by pollinosis.